深冷处理对高氮M42高速钢组织与性能的影响

Effect of cryogenic treatment on microstructure and properties of high-nitrogen M42 high-speed steel

以无氮和高氮M42高速钢为对象,研究了深冷处理对显微组织、硬度、红硬性和压缩性能的影响规律。结果表明:无氮和高氮M42高速钢的淬火组织主要由马氏体、残余奥氏体以及未溶的M2C和M6C碳化物组成,氮的添加将增加残余奥氏体含量;深冷处理能促进残余奥氏体向马氏体转变,且随着深冷温度降低和深冷时间延长,残余奥氏体转变更加充分;深冷处理并回火后残余奥氏体基本转变。深冷处理可以显著提高实验钢的回火硬度和红硬性,且随深冷温度的降低和时间的延长逐渐增加,但对其室温压缩性能影响不大。优选的深冷工艺为-130或-196℃深冷4 h,能提高钢的回火硬度约0.9HRC~1.2HRC、红硬性约1.3HRC~1.8HRC。氮合金化能显著提高钢的硬度、红硬性和抗压强度,但略微降低压缩断裂应变。

The effect of cryogenic treatment on the microstructure,hardness,red-hardness and room temperature compressive properties of nitrogen-free and high-nitrogen M42 high-speed steels(HSSs)was studied.The results show that the microstructure of both nitrogen-free and high-nitrogen M42 HSSs after quenching mainly consists of martensite,retained austenite and undissolved M_(2)C and M_(6)C carbides,and the addition of nitrogen increases the content of retained austenite.The cryogenic treatment after quenching promotes the transformation of retained austenite to martensite,and the retained austenite transforms more fully with the reduction of cryogenic temperature and the extension of time.The retained austenite is completely transformed into martensite during tempering after cryogenic treatment.The hardness and red-hardness after tempering of experimental steels are significantly improved by cryogenic treatment and gradually increase with the decrease of cryogenic temperature and the increase of cryogenic time.However,the cryogenic treatment has little effect on the room-temperature compressive properties of steels.The preferred cryogenic process is-130℃ or-196℃ for 4h,which increases the tempering hardness steels by about 0.9HRC-1.2HRC and the red-hardness by about 1.3HRC-1.8HRC.Nitrogen-alloying significantly increases the hardness,red-hardness and compressive strength,whereas slightly reduces the compressive fracture strain.